1. Field of the Invention
The present invention relates to a light emitting diode having an AlxGa1−xN buffer layer and a method of fabricating the same, and more particularly, to a light emitting diode having an AlxGa1−xN buffer layer, wherein between a substrate and a first conductive semiconductor layer, the AlxGa1−xN (0≦x≦1) buffer layer having the composition ratio x of Al decreasing from the substrate to the first conductive semiconductor layer is interposed to reduce lattice mismatch between the substrate and the first conductive semiconductor layer, and a method of fabricating the same.
2. Discussion of the Background
A light emitting diode (LED) is a photoelectric conversion semiconductor device having a structure in which an N-type semiconductor and a P-type semiconductor are joined to each other, and emits light by recombination of electrons and holes. The LED has been widely used as a display device and a backlight. Further, since the LED has lower power consumption and longer lifespan as compared with bulbs or fluorescent lamps, the applications of the LED are expanded to general illumination while substituting for incandescent lamps and fluorescent lamps.
In a light emitting diode, a sapphire substrate having good stability has been generally used as a substrate that serves as a base of the light emitting diode. An AlxInyGa1−x−yN semiconductor layer (0≦x,y,x+y≦1), i.e., a GaN-based semiconductor layer, is grown on the substrate. Particularly, in case of green and blue light emitting diodes, there are many light emitting diodes using the GaN-based semiconductor layer having a higher band gap.
However, the GaN-based semiconductor layer grown on the sapphire substrate has a problem in that it has a higher defect density due to lattice mismatch between the GaN-based semiconductor layer and the sapphire substrate, resulting in problems of deterioration of the reliability, productivity and electrical properties of the light emitting diode.
In order to solve these problems, a conventional light emitting diode has been fabricated by using a method in which a GaN buffer layer is grown on a sapphire substrate and a doped GaN-based conductive semiconductor layer is then grown on the GaN buffer layer.